Air conditioner and method of controlling the same

ABSTRACT

An air conditioner and a method of operating the same are provided. The air conditioner may include a plurality of compressors, each of which may include a casing that stores oil therein, and an oil level detecting device that detects an oil level within the casing. Once oil levels within each of the plurality of compressors are detected, oil may be redistributed between the plurality of compressors without interrupting a normal operation of the air conditioner. Oil may be transferred from a compressor having an oil level greater than a desired amount to a compressor having an oil level less than the desired amount. If there remains a compressor that contains an insufficient amount of oil after redistributing the oil among the plurality of compressors, an oil collecting operation may be performed.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. §119 to KoreanApplication No. 10-2010-0030120 filed in Korea on Apr. 1, 2010, whoseentire disclosure(s) is/are hereby incorporated by reference.

BACKGROUND

1. Field

An air conditioner and a method of controlling the same are disclosedherein.

2. Background

Air conditioner and methods of controlling the same are known. However,they suffer from various disadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the followingdrawings in which like reference numerals refer to like elements, andwherein:

FIG. 1 is a schematic diagram of an air conditioner having a pluralityof compressors according to an embodiment;

FIG. 2 is a cross-sectional view of internal structure of a compressorand an oil separator of FIG. 1;

FIG. 3 is a flow chart of a method of operating the air conditioner ofFIG. 1;

FIG. 4 is a schematic diagram of an air conditioner having a pluralityof compressors according to another embodiment;

FIG. 5 is a flow chart of a method of operating the air conditioner ofFIG. 4;

FIG. 6 is a schematic diagram of an air conditioner having a pluralityof compressors according to another embodiment; and

FIG. 7 is a flow chart of a method of operating the air conditioner ofFIG. 6.

DETAILED DESCRIPTION

A compressor, as broadly described and embodied herein, may include adrive motor that provides a driving force to a compression device tocompress refrigerant while operating in conjunction with the drivemotor. The compressor may be categorized as, for example, areciprocating type, a scroll type, a rotary type, or a vibration type,depending on the method by which the refrigerant is compressed.Reciprocating type, scroll type, and rotary type compressors use arotary motion of the drive motor, while vibration type compressors use areciprocating motion of the drive motor.

The drive motor of a rotary type compressor may be provided with acrankshaft that transfers the rotary motion of the drive motor to thecompression device. For example, the drive motor of the rotarycompressor may include a stator fixed to a container or case, a rotorpositioned in the stator with a predetermined gap therebetween to rotatein interaction with the stator, and a crankshaft connected to the rotorto transfer rotary power to the compression device. In addition, thecompression device may be combined with the crankshaft to suction,compress, and discharge refrigerant while rotating inside a cylinder. Aplurality of bearing members may be provided to form a compression spacebetween the crank shaft and the compression device, and may also supportthe compression device.

In the compressor having the foregoing structure, the refrigerant may becompressed by rotating the compression device with rotary motiongenerated by the drive device. The compressor may be provided with anoil supply device to supply oil to the compression device thatfacilitates the rotation of the compression device as well as easilydissipates heat generated during operation of the drive device. The oilsupply device may be provided at a lower end portion of the crankshaft.The oil may be stored in a lower portion of the container or case, andmay be pumped through an oil flow path formed inside the crankshaft bythe rotation of the crankshaft. The pumped oil may then be supplied toeach component inside the compressor.

In compressors of various air conditioning systems, the oil flow path,or pipe, in which the working fluid flows, may be lengthened, requiringan increased amount of oil to operate the compressor. Thus, it may bedifficult to estimate when, where, and how much oil will remain, andaccordingly, it may be difficult to maintain the oil level inside eachcompressor in an appropriate condition or level. As a result, the oillevel in the oil storage space may become irregular and may vary outsideof acceptable levels during operation of the respective compressor, evenwhen the oil levels were within a suitable range at an initial stage ofthe operation.

Therefore, it may be necessary to continuously check the oil levelinside each compressor during operation of the air conditioner. If it isdetermined that the oil level is not in an appropriate condition, thenan oil collecting operation to add oil to the compressor may beperformed. However, it may be difficult to manually check the oil levelin each compressor, and therefore, the oil collecting operation may beperformed at predetermined intervals regardless of the actual oil level.Performing the oil collecting operation irrespective of the actual oillevels may be inefficient as energy may be wasted during unnecessary oilcollecting operations.

To overcome this problem, an oil level sensor or detecting device may beprovided in the compressor to measure the oil level to determine whetheran oil collecting operation is necessary. One such oil detecting devicefor a compressor is disclosed in co-pending application Ser. No ______(Attorney Docket No. P-1047), which is hereby incorporated by reference.Thus, the number of unnecessary oil collecting operations may bereduced, and may result in decreased energy consumption as well asdecreased compressor downtime.

FIG. 1 is a schematic diagram of an air conditioner having a pluralityof compressors according to an embodiment. Referring to FIG. 1, the airconditioner may include a plurality of compressors 100, 100′, 100″, allof which may have the same structure. Each compressor may include afirst suction pipe 110, through which refrigerant may flow, and a secondsuction pipe 112, 112′, 112″ branched off from the first suction pipe110 to each respective compressor 100, 100′, 100″. In addition,compressed refrigerant may be discharged from each compressor 100, 100′,100″ through respective discharge pipes 114, 114′, 114″.

Oil may be stored inside the compressor, which may serve to lowerfriction within the compressor during operation. Further, an oil leveldetecting sensor 102, 102′, 102″ that detects the level of the oil maybe provided at a lateral surface of each respective compressor. A firstoil return pipe 120, 120′, 120″ may also be provided at each compressor,that connects each respective compressor 100, 100′, 100″ to the firstsuction pipe 110 to redistribute the oil received from the first oilreturn pipe 120, 120′, 120″. The first oil return pipes 120, 120′, 120″may be provided with capillary tubes 124, 124′, 124″, respectively, thatreduce the pressure of oil. Moreover, the first oil return pipes 120,120′, 120″ may be provided with solenoid valves 126, 126′, 126″,respectively, to open or close the first oil return pipes 120, 120′,120″.

The discharge pipes 114, 114′, 114″, which each discharges a mixture ofoil and refrigerant from the respective compressor, may be provided withoil separators 130, 130′, 130″, respectively. The oil separators 130,130′, 130″, which separate the discharged oil from the refrigerant, maytransfer the separated oil through second oil separators 132, 132′,132″, respectively, to the first suction pipe 110. The separatedrefrigerant, and any remaining oil, may be discharged from the oilseparators 130, 130′, 130″ to a 4-way valve 140. Thus, the dischargedoil may be separated from the refrigerant by the oil separators 130,130′, 130″ and resupplied to the compressors 100, 100′, 100″ through thefirst suction pipe 110 and the second suction pipes 112, 112′, 112″.

The 4-way valve 140 may include, for example, three discharge ports,which may be connected to an accumulator 180, an outdoor-side heatexchanger 150, and one or more indoor-side heat exchanger(s) 170, 170′,170″, respectively. The air conditioner may provide either cooling orheating based on a switching state of the 4-way valve 140. Simply forease of explanation, the 4-way valve as shown in FIG. 1 is configured toprovide cooling to the indoor-side.

In the embodiment of FIG. 1, the refrigerant discharged from the 4-wayvalve 140 may be passed through the outdoor-side heat exchanger 150 andexpansion apparatuses 160, 160′, 160″. The refrigerant may then bepassed into the indoor-side heat exchangers 170, 170′, 170″, which usethe refrigerant to lower an indoor temperature. The refrigerant may thenpass through the 4-way valve 140 into the accumulator 180. Oncerefrigerant remaining in a liquid state is separated from refrigerant ina gaseous state, the accumulator 180 may pass the gaseous refrigerant tothe first suction pipe 110.

FIG. 2 is a cross-sectional view of internal structure of a compressorand an oil separator of FIG. 1. Compressors 100′, 100″ and oilseparators 130′, 130″ of FIG. 1 may have the same structure ascompressor 100 and oil separator 130 of FIG. 1. Therefore, repetitivedescription of the compressors 100′, 100″ and oil separators 130′, 130″has been omitted hereinafter.

Simply for ease of explanation, embodiments are described herein in theform of a scroll compressor. However, embodiments are not limitedthereto and may be applied to or employ any type of compressor in whichoil is stored inside of the compressor. Referring to FIG. 2, a mainframe 20 and a sub frame 30 may be provided inside a container or case10, and a drive motor 40, which is a driving device, may be providedbetween the main frame 20 and sub frame 30. A compression device thatcompresses refrigerant may be combined with the drive motor 40. Thecompression device may include a fixed scroll 50 and an orbiting scroll60, which may be provided at an upper side of the main frame 20.Further, a suction port SP may be formed on the container 10 and may beconnected to the second suction pipe 112. The compressed refrigerant maybe supplied from the compressor 100 to the oil separator 130 via thedischarge pipe 114.

The oil separator 130 may include a discharge pipe 131 at an upper sidethereof and discharge port 133 at a lower side thereof. The dischargeport 133 may be connected to the second oil return pipe 132. Thedischarge pipe 131 may extend to a middle portion of the oil separator130, and thus, may lengthen a flow path of the compressed refrigerant inthe oil separator 130. Accordingly, as compressed refrigerant isdischarged from the discharge pipe 131 to the 4-way valve 140, any oilthat remains in the compressed refrigerant may be separated therefromand collected in a lower portion of the oil separator 130. The separatedoil, once collected, may be discharged from the oil separator 130 viathe discharge port 133 to the second oil return pipe 132.

The drive motor 40 may include a stator 41, which may be wound with acoil, a rotor 42 rotatably inserted in the stator 41, and a rotatingshaft 43 attached to a center of the rotor 42 that transfers rotaryforce to a compression mechanism. A driving pin portion 44 may be formedto protrude at an upper end of the rotating shaft 43. The driving pinportion 44 may be formed adjacent to a rotational axis of the rotatingshaft 43. That is, the driving pin portion 44 may be positioned awayfrom a rotational center of the rotating shaft 43.

The compressor 100 may further include the fixed scroll 50, which may befixed to an upper surface of the main frame 20, the orbiting scroll 60,which may be placed on an upper surface of the main frame 20 and engagedwith the fixed scroll 50, and an Oldham ring 70 disposed between theorbiting scroll 60 and the main frame 20 to prevent the rotation of theorbiting scroll 60. A fixed wrap 51 may be spirally wound and formed onthe fixed scroll 50. Further, an orbiting wrap 61 may be spirally woundand formed on the orbiting scroll 60. The fixed wrap 51 together withthe orbiting wrap 61 may form a compression chamber (P). A boss portion62 may protrude at a bottom surface of the orbiting scroll 60, forexample, a lateral surface opposite the orbiting wrap 61. The bossportion 62 may engage the rotating shaft 43 to receive a rotary forcetherefrom.

A sliding bush 63 may be combined with the driving pin portion 44 of therotating shaft 43 to slide in a radial direction. The sliding bush 63may then be combined with the boss portion 162 of the orbiting scroll 60to slide in a rotating direction. An external diameter of the slidingbush 63 may be formed to be the same as an internal diameter of the bossportion 62 of the orbiting scroll 60, to thereby reduce friction betweenthe rotating shaft 43 and the orbiting scroll 60. Further, a main framebush 22 may be provided on an inside surface of the main frame 120 toreduce friction between the rotating shaft 43 and main frame 20. Oil maybe supplied by an oil feeder 180 provided at a lower end portion of therotating shaft 43 to lubricate each of the bushes 22, 63.

The oil may be stored in an oil storage space formed by an inner surfaceof a base 12 of the container 10. The oil may be pumped from the oilstorage space and supplied to the compression device through an oil flowpath 43 a formed inside the rotating shaft 43. The oil feeder 80, whichmay be provided at a lower end portion of the oil flow path 43 a, mayrotate with the rotating shaft 43 to pump the oil from the oil storagespace into the oil flow path 43 a. The pumped oil may then be suppliedto the compression device positioned at an upper portion of the oil flowpath 43 a.

In order for the oil to be supplied by the oil feeder 80, the oil shouldbe maintained at appropriate levels inside the container 10. However,the level of oil may vary during operation of the compressor 100. Thevariation of oil level may be an absolute variation due to, for example,loss or leakage of oil, or a temporary variation in which the oil levelmay temporarily increase or decrease during operation based on changesin an operational speed of the compressor 100. In either case, the oillevel should be maintained in an appropriate condition, for example,within an acceptable range, during the operation of the compressor toensure normal operation. Accordingly, an oil level detecting sensor 102may be provided to detect the oil level inside the container 10 in realtime.

The oil level detecting sensor 102 may include a pair of electrodes 102a, which may protrude inside the container 10. A supporting plate 102 bmay be provided to support the pair of electrodes 102 a and allow themto pass through the container 10 into the compressor 100. The supportingplate 102 b may be attached to a side wall of the container 10 by, forexample, welding or another appropriate method of attaching. Further,the supporting plate 102 b may be attached to the container 10 so as tobe flush with an outer surface of the container 10. A flange 102 c maybe formed that protrudes from an outer circumference of the supportingplate 102 b. A flange anchoring portion 16, which may have a diametergreater than a diameter of the mounting hole 14, may be formed at anouter circumference of the mounting hole 14. When the supporting plate102 b is inserted into the mounting hole 14, the flange 102 c may beseated on the flange anchoring portion 16 and may be attached to thecontainer 10. Accordingly, the supporting plate 102 b may be mounted tothe container 10 at a desired position.

FIG. 3 is a flow chart of a method of operating the air conditioner ofFIG. 1. Referring to FIG. 3, once operation of the plurality ofcompressors is initiated, the oil level H of each compressor may firstbe detected, in step S01. Based on the detection result, it may then bedetermined whether the oil level H of each compressor is over a presetlevel for the respective compressor, in step S02. If the oil level H ofall of the compressors is over the respective preset level, normaloperation of the plurality of compressors may be initiated, in step S07.If the oil level H of some or all of the plurality of compressors is notover the preset level, then a number of compressors may be determined inwhich the oil level H is less than or equal to the respective presetlevel, in step S03. If the number of compressors having a relatively lowoil level H is greater than a predetermined number of compressors, forexample, the number of compressors is greater than one, then an oilcollection operation may be initiated, in step S08. When the number ofcompressors requiring additional oil is two or more, it may be difficultto adjust the oil level in each compressor to be over the preset levelswithout an oil collection operation. Further, when the number ofcompressors is two or more, a large amount of time may be required totransfer oil between the plurality of compressors. In this case, the oilcollection operation may be required. The predetermined number ofcompressors may be set to any number according to the number ofcompressors included in the air conditioner.

The oil collecting operation may transfer oil remaining inside the airconditioner, for example, in the foregoing indoor/outdoor-side heatexchanger or pipes, to the compressor(s) having a low oil level. Duringthe oil collecting operation, the expansion apparatus 160, 160′, 160″ ofeach indoor unit and each indoor-side heat exchanger may be fullyopened, an operation of the indoor unit may suspended, and a flow ratein the pipes may be increased. The flow rate may be increased byoperating a greater number of compressors than during a normal operationor by increasing an operational speed of one or more of the compressors.

If the number of compressors in which the oil level H is less than orequal to the respective preset level is determined to be less than orequal to the predetermined number in step S03, for example, the numberof compressors is equal to one, the process may move to step S04. Instep S04, the oil levels H in the compressors may be adjusted withoutperforming an oil collecting operation. For example, a solenoid valve ofthe compressor in which the oil level H is greater than the preset levelmay be opened, and a solenoid valve of the compressor in which the oillevel H is less than the preset level may be closed, in step S04. Forexample, referring to FIG. 1, if the compressor 100 has a sufficient oillevel and the compressor 100″ has a relatively low oil level, thesolenoid valve 126 may be opened and the solenoid valve 126″ may beclosed.

With the solenoid valves configured as above, a normal operation of thecompressors may be carried out for a predetermined period of time, forexample, approximately five minutes, in step S05. During the normaloperation of the compressors, oil may be collected from the compressor100 having a sufficient oil level, which may then be uniformlydistributed and supplied to each compressor through the first and thesecond suction pipes. However, as the solenoid valve 112″ of thecompressor 100″ having a relatively low oil level is closed, oil is notcollected from compressor 100″. The oil level in the compressor 100″ maytherefore gradually increase above the preset level. Accordingly, an oillevel of a compressor having insufficient oil may be increased above thepreset level when a total amount of oil stored in the air conditioner issufficient.

However, it may be difficult to adjust the oil level of each compressorover a desired level in spite of the foregoing process when a totalamount of oil remaining inside all of the compressors, for example, atotal amount of oil in the air conditioning system, is insufficient tobe redistributed. Thus, as previously described, the normal operationmay be carried out for the predetermined period of time, for example,approximately 5 minutes, in step S05. Thereafter, the oil levels H ofthe compressors may be checked again, and if the oil level H of all ofthe compressors is over each respective preset level, in step S06 thecompressors may return to normal operation, in step S06. Otherwise, ifthe oil level H of all of the compressors is not above the respectivepreset levels, the oil collecting operation may be performed, in stepS08.

FIG. 4 is a schematic diagram of an air conditioner according to anotherembodiment. Referring to FIG. 4, the air conditioner may temporarilystore oil collected from each compressor 100, 100′, 100″ in an oilreservoir 128 through a first oil return pipe 120, 120′, 120″. The oilreservoir 128 may include an oil level detecting sensor 128 a thatdetects an oil level inside the oil reservoir 128 and a valve 128 b thatcontrols a flow of oil discharged from the oil reservoir 128. The oilreservoir 128 may store oil exceeding a preset level received from eachof the compressors 100, 100′, 100″, and may then supply the storedexcess oil to a compressor having a low oil level through the firstsuction pipe 110 and the second suction pipes 112, 112′, 112″.

FIG. 5 is a flow chart of a method of operating the air conditioner ofFIG. 4. After detecting an oil level H of each compressor, in step S10,a number of compressors in which the oil level H is lower than or equalto a respective preset level is determined. If the number of compressorsis less than or equal to a predetermined number, for example, thepredetermined number is one, in step S11, then it may be determinedwhether all of the compressors have sufficient amounts of oil, in stepS12. If the oil level H of all of the compressors is above therespective preset level, then the compressors are operated in normaloperation, in step S16. If it is determined in step S12 that the oillevel H of all of the compressors is not over the respective presetlevel, then a solenoid valve 126 of each compressor in which the oillevel H is greater than a respective preset level may be opened, and avalve 126″ of the compressor in which H is less than or equal to thedesired level may be closed, in step S13.

A normal operation of the compressors may be carried out in this statefor a predetermined amount of time, for example, about five minutes, instep S14. Then, oil collected from each of the compressors having asufficient amount of oil may be uniformly distributed and supplied toall compressors through the first and the second suction pipes. However,oil is not collected from a compressor for which the solenoid valve isclosed. Further, oil may be collected again even if it is supplied to acompressor for which the solenoid valve is open, thereby maintaining theoil level over a preset level. Accordingly, the oil levels in each ofthe compressors may be maintained over a preset level when the totalamount oil stored by the compressors is sufficient.

However, it may be difficult to adjust the oil level of a compressor tobe over a preset level in spite of this process when the total amount ofoil remaining inside the compressors is insufficient. Thus, aspreviously described, a normal operation of the compressors may becarried out for the predetermined period of time, for example,approximately 5 minutes, in step S14. Then, the oil level of each of thecompressors may be checked again, and in step S16, if the oil level H ofall compressors is over each respective preset level, in step S15, anormal operation may be carried out. Otherwise, an oil collectingoperation may be performed, in step S20.

In step S11, if the number of the compressors having a relatively lowoil level (H is below respective preset level) is greater than thepredetermined number, for example, the predetermined number is one thenan oil level of the oil reservoir (H_(R)) may be detected, in step S17.After detecting the oil level H_(R) of the oil reservoir, the oilcollecting operation may be performed, in step S20, if the oil levelH_(R) of the oil reservoir is lower than or equal to a preset level ofthe reservoir, in step S18. Otherwise, if H_(R) is greater than thepreset level, the reservoir valve 128 b may opened, in step S19, and thesolenoid valves 126, 126′, 126″ of the compressors may be configured aspreviously described to increase the oil levels in the compressorshaving oil levels below preset levels, in step S13.

FIG. 6 is a schematic diagram of an air conditioner according to anotherembodiment. Referring to FIG. 6, a plurality of compressors 200, 200′,200″ may share one oil separator 230. An oil level detecting sensor 231that detects an oil level H_(S) inside the oil separator 230 may beprovided in the oil separator 230. Further, a second oil return pipe 232that supplies the oil stored in the oil separator 230 to the compressors200, 200′, 200″ may be provided. The second oil return pipe 232 may beconnected to oil replenishing pipes 234, 234′, 234″, which may beconnected to the second suction pipes 112, 112′, 112″ of thecompressors, respectively. In addition, the oil replenishing pipes 234,234′, 234″ may be provided with valves 236, 236′, 236″ that control theflow of oil to each respective compressor 200, 200′, 200″.

The valves 236, 236′, 236″ may be switched according to a detectionresult of corresponding oil level detecting sensors 102, 102′, 102″. Forexample, if additional oil is not required in compressors 200, 200′because the respective oil levels are greater than a respective presetlevel, corresponding valves 236, 236′ may be closed. However, ifadditional oil is required in compressor 200″ because a correspondingoil level is less than a preset level, valve 236″ may be opened tosupply oil stored in the oil separator 230 to compressor 200″.

FIG. 7 is a flow chart of a method of operating the air conditioner ofFIG. 6. After detecting an oil level H of each compressor, in step S21,a number of compressors in which the oil level H is lower than or equalto a respective preset level is determined, in step S22. If the numberof compressors is less than or equal to a predetermined number, forexample, the predetermined number is one, then it is determined whetherall of the compressors have a sufficient amount of oil, in step S23. Ifthe oil level H of all of the compressors is above the respective presetlevels, then the compressors are operated in normal operation, in stepS27. If the oil level H of all of the compressors are not above thepreset levels, then the solenoid valve 236″ of the compressor in which His less than or equal to the preset level may be opened, and thesolenoid valve 236, 236′ of each of the compressors in which H isgreater than the respective preset level may be closed, in step S24.

Thereafter, normal operation may be carried out in this state for apredetermined amount of time, for example, about five minutes, in stepS25. The oil stored in the oil separator 230 may then be provided to thecompressor 200″ having the insufficient oil level during thepredetermined amount of time. Then, the oil level of all of thecompressors may be checked again, and if the oil level H of the allcompressors is over each respective preset level, in step S26, thecompressors may return to normal operation, in step S27. Otherwise, anoil collecting operation may be performed, in step S30.

Returning to step S22, if the number of the compressors in which the oillevel H is less than or equal to the respective preset level is greaterthan the predetermined number, for example, the number of compressors is2 or 3, then the oil level H_(S) of the oil separator 230 may bedetected, in step S28. After detecting the oil level H_(S), the oilcollecting operation may be performed, in step S30, if the oil levelH_(S) is lower than or equal to a preset level for the oil separator230, in step S29. Otherwise, if the oil level H_(S) is over the presetlevel, the valves of each compressor may be configured to add oil tocompressors having an oil level H less than or equal to the respectivepreset level, in step S24.

According to embodiments, an operating method for an air conditionerhaving multiple compressors is provided which may minimize an amount oftime required to perform an oil collection operation.

According to one embodiment, an operating method may be provided for anair conditioner, which may include a plurality of compressors, each ofwhich may include a casing that may store oil in an inner lower portionthereof and an oil level detecting device that detects the oil levelwithin the casing; at least one first heat exchanger that intakes aworking fluid from the plurality of compressors; at least one expansionunit; at least one second heat exchanger, through which the workingfluid may pass after the first heat exchanger; a first suction pipe, towhich the working fluid flows from the first or second heat exchanger;and a plurality of second suction pipes, which may be branched out fromthe first suction pipe and connected to each of the compressors. Themethod may include detecting an oil level of each of the compressors;distributing the oil in the compressor containing oil over a desiredlevel preset for each compressor toward the compressor containing oillower than a desired level preset for each compressor via the first andthe second suction pipes without passing through the first and thesecond heat exchanger; and performing an oil collecting operation in acase in which there may be a compressor containing oil lower than adesired level preset for each compressor after performing thedistributing.

According to this embodiment, the oil may be supplied to the compressorswith a relatively lower oil level from a compressor with a relativelyhigher oil level without performing an oil collecting operation.Therefore, it may be possible to supply oil to the compressor withoutstopping normal operation of the air conditioner, which may minimize anumber of the oil collecting operations.

The distributing may be performed for a predetermined period or untilall of the compressors have the desired oil level. However, there may bea limit as to an amount of time necessary to distribute the oil whenthere is not enough oil in the compressors to fill each compressor to arespective desired level preset for each compressor with the oil fromanother compressor.

The oil collecting operation may be performed prior to the distributingwhen a number of the compressors containing oil lower than a desiredlevel preset for each compressor is more than a predetermined number.For example, when there is not enough oil in the compressors to filleach compressor to a desired level preset for each compressor with theoil supply between the compressors, the oil distributing process may becancelled, and then the oil collecting operation may proceed.

Further, a first oil return pipe may be included that connects an insideof the casing of each compressor to the first suction pipe, and the oilin the compressor containing oil over a desired level preset for eachcompressor may be supplied to the first suction pipe via the first oilreturn pipe during the distributing. The oil supplied to the firstsuction pipe may be distributed to each of the compressors via thesecond suction pipe, and by performing such steps repeatedly, the oillevel in each of the compressors may remain over a desired level presetfor each compressor.

Further, the first oil return pipe of the compressor containing oillower than a desired level preset for each compressor may remain closedduring the distributing. Accordingly, the oil level may be recoveredquickly to the desired level since the oil in the compressor containingoil lower than a desired level preset for each compressor may not becollected from the compressor.

Additionally, at least one oil separator with a second oil return pipethat connects the oil separator and the first suction pipe may beincluded, and the oil collected in the oil separator may be supplied tothe first suction pipe via the second oil return pipe. The oil separatormay separate and store the oil from the mixed working fluid dischargedfrom the compressors, and the oil in the oil separator may be suppliedto the compressors to increase the oil level.

Here, the first oil return pipe may be further included, and it may bepossible to increase the oil supply to the compressor by connecting bothof oil separator and first oil return pipe to the first suction pipe.Further, additional oil storing devices, for example, an oil reservoir,may be included, and the oil collected from the compressors may bedistributed via the oil storing devices.

According to another embodiment, an operating method is provided for anair conditioner including a plurality of compressors, each of which mayinclude a casing that stores oil in on inner lower portion thereof, andan oil level detecting device that detects the oil level within thecasing; at least one oil storage that stores the oil from thecompressors; at least one first heat exchanger that intakes a workingfluid from the plurality of compressors; at least one expansion unit; atleast one second heat exchanger, through which the working fluid maypass after the first heat exchanger; a first suction pipe, to which theworking fluid flows from the first or second heat exchanger; and aplurality of second suction pipes branched from the first suction pipeand connected to each of the compressors. The method may includedetecting the oil level of each of the compressors and the oil storage;supplying the oil in the oil storage or the compressors containing oilover a desired level preset for each compressor to the compressorcontaining oil lower than a desired level preset for each compressor;and performing an oil collecting operation when there is a compressorcontaining oil lower than a desired level preset for each compressorafter performing the step of supplying.

The method may further include performing the oil collecting operationwhen a number of the compressors containing oil lower than a desiredlevel preset for each compressor is over a predetermined number and theoil level of the oil storage is lower than a desired level for the oilstorage.

Further, the oil in the oil storage may be supplied to the compressoronly when the oil level of the oil storage is over the desired level forthe oil storage. The oil storage may also include at least one oilseparator connected to the compressors. Additionally, the supplying maybe performed for a predetermined period or until all of the compressorshave the desired oil level.

According to another embodiment, an operating method is provided for anair conditioner which may include comprise at least one compressor withan oil level detecting device; an oil transferring device that transfersoil among the at least one compressor; a plurality of heat exchangersand an expansion unit that cooperate with the at least one compressor.The method may include detecting the oil level of each of thecompressors; transferring the oil from the compressors with relativelyhigher oil level to the compressors with a relatively lower oil level;and performing an oil collecting operation when a number of thecompressors with the oil level lower than a desired level preset foreach compressor is greater than a predetermined number.

The method may further include performing the oil collecting operationwhen a compressor containing oil lower than a desired level preset foreach compressor still remains even after transferring the oil for apredetermined time.

According to another embodiment, an operating method is provided for anair conditioner, which may include at least one compressor with an oillevel detecting unit; at least one oil storage that may stores the oilfrom the at least one compressor; an oil supplying device that suppliesthe oil of the oil storage to the at least one compressor; a pluralityof heat exchangers and expansion units that cooperate with the at leastone compressor. The method may include detecting the oil level of eachcompressor and the oil storage; supplying the oil from a compressorcontaining oil over a desired level preset for each compressor or theoil storage toward a compressor containing oil lower than a desiredlevel preset for each compressor; and performing an oil collectingoperation when a number of the compressors containing oil lower than adesired level preset for each compressor is greater than a predeterminednumber and the oil level of the oil storage is lower than a desiredlevel for the oil storage.

The method may further include supplying the oil from the oil storagetoward the compressor containing oil lower than a desired level presetfor each compressor when the number of the compressors containing oillower than a desired level preset for each compressor is greater thanthe predetermined number and the oil level of the oil storage is overthe desired level for the oil storage. According to this embodiment, anumber of oil collecting operations may be minimized by circulating theoil in the compressors among the other compressors.

According to another embodiment, there is provided an operating methodfor an air conditioner, the air conditioner including a plurality ofcompressors, ea h of which includes a casing that stores oil in an innerlower portion thereof and an oil level detecting device that detects anoil level in the casing; at least one first heat exchanger that intakesa working fluid from the plurality of compressors; at least oneexpansion device; at least one second heat exchanger, through which theworking fluid passes after passing through the at least one first heatexchanger; a first suction pipe, through which the working fluid flowsfrom the at least one first heat exchanger or the at least one secondheat exchanger; and a plurality of second suction pipes branched fromthe first suction pipe and then connected to each of the compressors,wherein the method may include detecting an oil level of each of theplurality of compressors; distributing oil in a first compressor of theplurality of compressors containing oil over a first preset level forthe first compressor toward a second compressor of the plurality ofcompressors containing oil lower than a second preset level for thesecond compressor via the first and the second suction pipes withoutpassing through the at least one first exchanger and the at least onesecond heat exchanger when a number of the plurality of compressorscontaining oil lower than the preset level for the respective compressoris less than or equal to a predetermined number; and performing an oilcollecting operation if there exists a compressor containing oil lowerthan a preset level for that compressor after performing thedistributing or if the number of the plurality of compressors containingoil lower than the preset level for the respective compressor is greaterthan the predetermined number.

The preset level of each of the plurality of compressors may be all thesame or all different. Alternatively, the preset level of at least twoof the plurality of compressors may be the same or different.

The distributing may be performed for a predetermined period of time, atpredetermined time intervals, or until all of the plurality ofcompressors have at least the preset level for the respectivecompressor. Further, each of the plurality of compressors may include afirst oil return pipe that connects the casing of the respectivecompressor to the first suction pipe, and oil in the respectivecompressor containing oil over the preset level for the respectivecompressor may be supplied to the first suction pipe via the first oilreturn pipe during the distributing. Furthermore, the first oil returnpipe connected to a compressor containing oil lower than a preset levelfor each compressor may remain closed during the distributing.

The air conditioner may further include at least one oil separatorhaving a second oil return pipe that connects the oil separator and thefirst suction pipe, and the oil collected in the oil separator may besupplied to the first suction pipe via the second oil return pipe duringthe step of distributing.

The at least one oil separator may receive a mixture of oil and workingfluid from at least one of the plurality of compressors through an oildischarge pipe. The at least one oil separator may also store the oilfrom the plurality of compressors and, if the number of the plurality ofcompressors containing oil lower than the preset level for therespective compressor is greater than the predetermined number, themethod may further include detecting an oil level of the at least oneoil separator; if the oil level of the at least one oil separator isless than a preset level for the at least one oil separator, performingthe oil collecting operation; and if the oil level of the at least oneoil separator is greater than or equal to the preset level, opening avalve that allows the oil to flow into the compressor containing oillower than the preset level for the respective compressor.

The air conditioner may further include a plurality of oil separators,and wherein each of the plurality of compressors may discharge a mixtureof oil and working fluid to a respective one of the plurality of oilseparators, wherein the distributing may include distributing the oilstored in the at least one oil separator toward the second compressor ofthe plurality of compressors containing oil lower than the second presetlevel for the second compressor.

The air conditioner may further include a first oil return pipe thatconnects the casing of each compressor to the first suction pipe, andthe oil in the respective compressor containing oil over a desired levelpreset for each compressor and the oil in the oil separator may besupplied to the first suction pipe via the first and the second oilreturn pipe during the distributing. Additionally, the air conditionermay include at least one oil reservoir that stores the oil from theplurality of compressors and if the number of the plurality ofcompressors containing oil lower than the preset level for therespective compressor is greater than the predetermined number, themethod may further include detecting an oil level of the at least oneoil reservoir; if the oil level of the at least one reservoir is lessthan a preset level for the at least one oil reservoir, performing theoil collecting operation; and if the oil level of the at least onereservoir is greater than or equal to the preset level of the at leastone oil reservoir, opening a reservoir valve of the at least onereservoir as part of the distributing.

Each of the plurality of compressors may include a first oil return pipethat connects the casing of the respective compressor to the at leastone oil reservoir, wherein oil in the respective compressor containingoil over the preset level for the respective compressor may be suppliedto the at least one oil reservoir via the first oil return pipe. Thefirst oil return pipe connected to the compressor containing oil lowerthan a preset level for each compressor may remain closed during thedistributing. The at least one oil reservoir may function as an oilseparator, wherein the oil separator may receive a mixture of oil andworking fluid from at least one of the plurality of compressors throughan oil discharge pipe.

An operating method for an air conditioner may include a plurality ofcompressors, each having an oil level detecting device, an oiltransferring device that transfers oil among the plurality ofcompressors; and a plurality of heat exchangers and expansion devicesthat cooperate with the plurality of compressors. The method may furtherinclude detecting an oil level of each of the plurality of compressors;transferring oil from at least one compressor of the plurality ofcompressors with a relatively higher oil level to at least onecompressor of the plurality of compressors with a relatively lower oillevel when a number of the plurality of compressors containing oil lowerthan the preset level for the respective compressor is less than orequal to a predetermined number; and performing an oil collectingoperation if a number of compressors containing oil lower than a presetlevel for the respective compressor is greater than a predeterminednumber.

The method may further include performing the oil collecting operationwhen a compressor containing oil lower than the preset level is detectedafter transferring the oil for a predetermined period of time, whereinthe transferring may include transferring the oil without passingthrough the plurality of heat exchangers and expansion devices thatcooperate with the plurality of compressors, and closing an oil returnpipe connected to the compressor containing oil lower than the presetlevel for the respective compressor during the transferring.

An operating method for an air conditioner may include the airconditioner that includes a plurality of compressors, each having an oillevel detecting device, an oil transferring device that transfers oilamong the plurality of compressors, and a plurality of heat exchangersand expansion devices that cooperate with the plurality of compressors,the method including detecting an oil level of each of the plurality ofcompressors; transferring oil from at least one compressor of theplurality of compressors with a relatively higher oil level to at leastone compressor of the plurality of compressors with a relatively loweroil level when a number of the plurality of compressors containing oillower than the preset level for the respective compressor is less thanor equal to a predetermined number; storing oil from at least one of theplurality of compressors during a normal operation of the airconditioner in at least one oil reservoir or at least one oil separator;detecting an oil level of the at least one oil reservoir or the at leastone oil separator when the number of compressors containing oil lowerthan the preset level for the respective compressor is greater than thepredetermined number; performing an oil collecting operation when theoil level of the at least one oil reservoir or the at least one oilseparator is less than a preset level for the at least one oil reservoiror the at least one oil separator; and transferring the stored oil tothe at least one compressor of the plurality of compressors with therelatively lower oil level when the oil level of the at least one oilreservoir or the at least one oil separator is greater than or equal tothe preset level for the at least one oil reservoir or the at least oneoil seperator.

The at least one oil reservoir or the at least one oil separator mayinclude at least one oil separator, and wherein the at least one oilseparator receives a mixture of oil and working fluid from at least oneof the plurality of compressors through an oil discharge pipe. Themethod may further include separating the mixture of oil and workingfluid at the at least one oil separator, and storing the separated oiland transferring the separated working fluid to the plurality of heatexchangers and expansion devices that cooperate with the plurality ofcompressors. Further, each of the plurality of compressors may include avalve that controls a flow of the stored oil from the at least one oilseparator to each respective compressor, and wherein the method furthercomprises opening the valve of the compressor containing oil lower thanthe preset level during the transferring of the stored oil.

The at least one oil reservoir or the at least one oil separator mayinclude at least one oil reservoir, wherein the at least one oilreservoir may function as an oil separator. Each of the plurality ofcompressors may include a valve that controls a flow of oil in the oilreturn pipe from each respective compressor to the at least one oilreservoir, and wherein the method may further include closing the valveof the compressor containing oil lower than the preset level during thetransferring. Each of the plurality of compressors may communicate witha respective one of a plurality of oil separators. Further, the at leastone oil reservoir may receives oil from at least one of the plurality ofcompressors through a respective oil return pipe that connects thecasing of each compressor to the at least one oil reservoir.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. An operating method for an air conditioner, the air conditionercomprising a plurality of compressors, each of which includes a casingthat stores oil in an inner lower portion thereof and an oil leveldetecting device that detects an oil level in the casing; at least onefirst heat exchanger that intakes a working fluid from the plurality ofcompressors; at least one expansion device; at least one second heatexchanger, through which the working fluid passes after passing throughthe at least one first heat exchanger; a first suction pipe, throughwhich the working fluid flows from the at least one first heat exchangeror the at least one second heat exchanger; and a plurality of secondsuction pipes branched from the first suction pipe and then connected toeach of the compressors, the method comprising: detecting an oil levelof each of the plurality of compressors; distributing oil in a firstcompressor of the plurality of compressors containing oil over a firstpreset level for the first compressor toward a second compressor of theplurality of compressors containing oil lower than a second preset levelfor the second compressor via the first and the second suction pipeswithout passing through the at least one first exchanger and the atleast one second heat exchanger when a number of the plurality ofcompressors containing oil lower than the preset level for therespective compressor is less than or equal to a predetermined number;and performing an oil collecting operation if there exists a compressorcontaining oil lower than a preset level for that compressor afterperforming the distributing or if the number of the plurality ofcompressors containing oil lower than the preset level for therespective compressor is greater than the predetermined number.
 2. Themethod of claim 1, wherein the preset level of each of the plurality ofcompressors are all the same or all different.
 3. The method of claim 1,wherein the preset level of at least two of the plurality of compressorsare the same or different.
 4. The method of claim 1, wherein thedistributing is performed for a predetermined period of time, atpredetermined time intervals, or until all of the plurality ofcompressors have at least the preset level for the respectivecompressor.
 5. The method of claim 1, wherein each of the plurality ofcompressors includes a first oil return pipe that connects the casing ofthe respective compressor to the first suction pipe, and wherein oil inthe respective compressor containing oil over the preset level for therespective compressor is supplied to the first suction pipe via thefirst oil return pipe during the distributing.
 6. The method of claim 5,wherein the first oil return pipe connected to a compressor containingoil lower than a preset level for each compressor remains closed duringthe distributing.
 7. The method of claim 1, wherein the air conditionerfurther comprises at least one oil separator having a second oil returnpipe that connects the oil separator and the first suction pipe, andwherein oil collected in the oil separator is supplied to the firstsuction pipe via the second oil return pipe during the distributing. 8.The method of claim 7, wherein the at least one oil separator receives amixture of oil and working fluid from at least one of the plurality ofcompressors through an oil discharge pipe.
 9. The method of claim 7,wherein the at least one oil separator stores the oil from the pluralityof compressors and if the number of the plurality of compressorscontaining oil lower than the preset level for the respective compressoris greater than the predetermined number, the method further comprises:detecting an oil level of the at least one oil separator; if the oillevel of the at least one oil separator is less than a preset level forthe at least one oil separator, performing the oil collecting operation;and if the oil level of the at least one oil separator is greater thanor equal to the preset level, opening a valve that allows the stored oilto flow into the compressor containing oil lower than the preset levelfor the respective compressor.
 10. The method of claim 1, wherein theair conditioner further comprises a plurality of oil separators, andwherein each of the plurality of compressors discharges a mixture of oiland working fluid to a respective one of the plurality of oilseparators.
 11. The method of claim 10, wherein the distributingincludes distributing the oil stored in the at least one oil separatortoward the second compressor of the plurality of compressors containingoil lower than the second preset level for the second compressor. 12.The method of claim 1, wherein the air conditioner further comprises afirst oil return pipe that connects the casing of each compressor to thefirst suction pipe, and wherein oil in the respective compressorcontaining oil over a preset level for each compressor and the oil inthe oil separator are supplied to the first suction pipe via the firstand second oil return pipes during the distributing.
 13. The method ofclaim 1, wherein the air conditioner further comprises at least one oilreservoir that stores the oil from the plurality of compressors and ifthe number of the plurality of compressors containing oil lower than thepreset level for the respective compressor is greater than thepredetermined number, the method further comprises: detecting an oillevel of the at least one oil reservoir; if the oil level of the atleast one reservoir is less than a preset level for the at least one oilreservoir, performing the oil collecting operation; and if the oil levelof the at least one reservoir is greater than or equal to the presetlevel of the at least one oil reservoir, opening a reservoir valve ofthe at least one reservoir as part of the distributing.
 14. The methodof claim 13, wherein each of the plurality of compressors includes afirst oil return pipe that connects the casing of the respectivecompressor to the at least one oil reservoir, and wherein oil in therespective compressor containing oil over the preset level for therespective compressor is supplied to the at least one oil reservoir viathe first oil return pipe.
 15. The method of claim 14, wherein the firstoil return pipe connected to the compressor containing oil lower than apreset level for each compressor remains closed during the distributing.16. The method of claim 13, wherein the at least one oil reservoirfunctions as an oil separator.
 17. The method of claim 16, wherein theoil separator receives a mixture of oil and working fluid from at leastone of the plurality of compressors through an oil discharge pipe. 18.An operating method for an air conditioner, the air conditionercomprising a plurality of compressors, each having an oil leveldetecting device, an oil transferring device that transfers oil amongthe plurality of compressors, and a plurality of heat exchangers andexpansion devices that cooperate with the plurality of compressors, themethod comprising: detecting an oil level of each of the plurality ofcompressors; transferring oil from at least one compressor of theplurality of compressors with a relatively higher oil level to at leastone compressor of the plurality of compressors with a relatively loweroil level when a number of the plurality of compressors containing oillower than the preset level for the respective compressor is less thanor equal to a predetermined number; and performing an oil collectingoperation if a number of compressors containing oil lower than a presetlevel for the respective compressor is greater than a predeterminednumber.
 19. The method of claim 18, wherein the method further comprisesperforming the oil collecting operation when a compressor containing oillower than the preset level is detected after transferring the oil for apredetermined period of time.
 20. The method of claim 18, wherein thetransferring comprises transferring the oil without passing through theplurality of heat exchangers and expansion devices that cooperate withthe plurality of compressors.
 21. The method of claim 20, wherein themethod further comprises closing an oil return pipe connected to thecompressor containing oil lower than the preset level for the respectivecompressor during the transferring.
 22. An operating method for an airconditioner, the air conditioner comprising a plurality of compressors,each having an oil level detecting device, an oil transferring devicethat transfers oil among the plurality of compressors, and a pluralityof heat exchangers and expansion devices that cooperate with theplurality of compressors, the method comprising: detecting an oil levelof each of the plurality of compressors; transferring oil from at leastone compressor of the plurality of compressors with a relatively higheroil level to at least one compressor of the plurality of compressorswith a relatively lower oil level when a number of the plurality ofcompressors containing oil lower than the preset level for therespective compressor is less than or equal to a predetermined number;storing oil from at least one of the plurality of compressors during anormal operation of the air conditioner in at least one oil reservoir orat least one oil separator; detecting an oil level of the at least oneoil reservoir or the at least one oil separator when the number ofcompressors containing oil lower than the preset level for therespective compressor is greater than the predetermined number;performing an oil collecting operation when the oil level of the atleast one oil reservoir or the at least one oil separator is less than apreset level for the at least one oil reservoir or the at least one oilseparator; and transferring the stored oil to the at least onecompressor of the plurality of compressors with the relatively lower oillevel when the oil level of the at least one oil reservoir or the atleast one oil separator is greater than or equal to the preset level forthe at least one oil reservoir or the at least one oil separator. 23.The method of claim 22, wherein the at least one oil reservoir or the atleast one oil separator comprises at least one oil separator, andwherein the at least one oil separator receives a mixture of oil andworking fluid from at least one of the plurality of compressors throughan oil discharge pipe.
 24. The method of claim 23, wherein the methodfurther comprises separating the mixture of oil and working fluid at theat least one oil separator, and storing the separated oil andtransferring the separated working fluid to the plurality of heatexchangers and expansion devices that cooperate with the plurality ofcompressors.
 25. The method of claim 23, wherein each of the pluralityof compressors includes a valve that controls a flow of the stored oilfrom the at least one oil separator to each respective compressor, andwherein the method further comprises opening the valve of the compressorcontaining oil lower than the preset level during the transferring ofthe stored oil.
 26. The method of claim 22, wherein the at least one oilreservoir or the at least one oil separator comprises at least one oilreservoir.
 27. The method of claim 26, wherein the at least one oilreservoir functions as an oil separator.
 28. The method of claim 27,wherein each of the plurality of compressors includes a valve thatcontrols a flow of oil in the oil return pipe from each respectivecompressor to the at least one oil reservoir, and wherein the methodfurther comprises closing the valve of the compressor containing oillower than the preset level during the transferring.
 29. The method ofclaim 26, wherein each of the plurality of compressors communicates witha respective one of a plurality of oil separators.
 30. The method ofclaim 26, wherein the at least one oil reservoir receives oil from atleast one of the plurality of compressors through a respective oilreturn pipe that connects the casing of each compressor to the at leastone oil reservoir.